In integrated circuit (IC) devices, resistive random access memory (RRAM) is an emerging technology for next generation non-volatile memory devices. RRAM is a memory structure including an array of RRAM cells each of which stores a bit of data using resistance values, rather than electronic charge. Particularly, each RRAM cell includes a resistive material layer, the resistance of which can be adjusted to represent logic “0” or logic “1.”
In advanced technology nodes, the feature size scales down and the size of memory devices is reduced accordingly. However, the reduction of the RRAM devices is limited due to the “forming” operation. In the “forming” operation, a high voltage is applied to the RRAM device to generate a conductive path in the resistive material layer of the RRAM device. The high “forming” voltage introduces reliability concern. Particularly, when a core device is formed as a selector device, the forming voltage is higher than the core device operation voltage. The selector device suffers the junction damage during the forming operation. Other solutions could not overcome the issue without introducing other side effects. For example, when the transistor off-state resistance is tuned higher, the voltage drop on the selector device during the forming operation is high, causing the damage to the selector device. When the transistor off-state resistance is tuned lower, the selector device may not function properly or have a high leakage current.
Accordingly, it would be desirable to provide an improved RRAM structure and a method of manufacturing thereof absent the disadvantages discussed above.